Porphyrin Sensitizers with Donor Structural Engineering for Superior Performance Dye‐Sensitized Solar Cells and Tandem Solar Cells for Water Splitting Applications
TL;DR: In this paper, the effect of the donor ability and the donor bulkiness on photovoltaic performances is investigated for establishing the structure-performance relationship in the platform of porphyrin-triple bond-benzothiadiazole-acceptor sensitizers.
Abstract: Zn(II)–porphyrin sensitizers, coded as SGT-020 and SGT-021, are designed and synthesized through donor structural engineering. The photovoltaic (PV) performances of SGT sensitizer-based dye-sensitized solar cells (DSSCs) are systematically evaluated in a thorough SM315 as a reference sensitizer. The effect of the donor ability and the donor bulkiness on photovoltaic performances is investigated for establishing the structure–performance relationship in the platform of porphyrin-triple bond-benzothiadiazole-acceptor sensitizers. By introducing a more bulky fluorene unit to the amine group in the SM315, the power conversion efficiency (PCE) is enhanced with the increased short-circuit current (Jsc) and open-circuit voltage (Voc), due to the improved light-harvesting ability and the efficient prevention of charge recombination, respectively. As a consequence, a maximum PCE of 12.11% is obtained for SGT-021, whose PCE is much higher than the 11.70% PCE for SM315. To further improve their maximum efficiency, the first parallel tandem DSSCs employing cobalt electrolyte in the top and bottom cells are demonstrated and an extremely high efficiency of 14% is achieved, which is currently the highest reported value for tandem DSSCs. The series tandem DSSCs give a remarkably high Voc value of >1.83 V. From this DSSC tandem configuration, 7.4% applied bias photon-to-current efficiency is achieved for solar water splitting.
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TL;DR: A critical assessment of the key components needed to scale up PEC water splitting systems such as materials efficiency, cost, elemental abundancy, stability, fuel separation, device operability, cell architecture, and techno-economic aspects of the systems are placed on.
Abstract: Solar water splitting is a promising approach to transform sunlight into renewable, sustainable and green hydrogen energy. There are three representative ways of transforming solar radiation into molecular hydrogen, which are the photocatalytic (PC), photoelectrochemical (PEC), and photovoltaic–electrolysis (PV–EC) routes. Having the future perspective of green hydrogen economy in mind, this review article discusses devices and systems for solar-to-hydrogen production including comparison of the above solar water splitting systems. The focus is placed on a critical assessment of the key components needed to scale up PEC water splitting systems such as materials efficiency, cost, elemental abundancy, stability, fuel separation, device operability, cell architecture, and techno-economic aspects of the systems. The review follows a stepwise approach and provides (i) a summary of the basic principles and photocatalytic materials employed for PEC water splitting, (ii) an extensive discussion of technologies, procedures, and system designs, and (iii) an introduction to international demonstration projects, and the development of benchmarked devices and large-scale prototype systems. The task of scaling up of laboratory overall water splitting devices to practical systems may be called “an artificial photosynthetic leaf-to-farm challenge”.
640 citations
TL;DR: In this paper, the effects of molecular structural engineering on the photophysical and electrochemical properties, photovoltaic parameters, and efficiency of dye-sensitized solar cells (DSSCs) are presented.
Abstract: Increasing energy consumption worldwide and environmental concerns about global warming have attracted great interest in the development of renewable and eco-friendly energy technologies. Dye-sensitized solar cells (DSSCs) have attracted considerable attention over the last 25 years since they offer possible low-cost conversion of photovoltaic energy. The sensitizer is the most important component of a DSSC, as it is largely responsible for light harvesting and charge separation, as well as the dye regeneration process. As a result, there have been tremendous research efforts in developing sensitizers. However, many challenges remain, and a deeper understanding of the design rules of DSSC sensitizers is required to obtain efficient and long-term stable DSSCs. The purpose of this review is to discuss recent progress and the rational design criteria used in the structural design of organic dyes and porphyrin photosensitizers for use in DSSCs. The effects of molecular structural engineering on the photophysical and electrochemical properties, photovoltaic parameters, and efficiency of DSSCs are presented.
219 citations
TL;DR: In this article, the alkylated thieno[3,2-b]indole (TI) moiety was used as the π-bridge unit to enhance the capability of the TBT used in organic sensitizers.
Abstract: The molecular design of organic sensitizers is one of the fundamental factors for high-efficiency dye-sensitized solar cells (DSSCs). In this study, we first utilize the alkylated thieno[3,2-b]indole (TI) moiety as the π-bridge unit to enhance the π-bridge capability of the thieno[3,2-b]benzothiophene (TBT) used in organic sensitizers. To improve the spectral response of the SGT-130 reference dye, we strategically designed and synthesized two novel TI-based organic sensitizers, SGT-136 and SGT-137, through a simple change of the π-bridge unit. By replacing the TBT with the alkylated TI moiety, SGT-136 and SGT-137 could have a red-shifted absorption band and upshifted highest occupied molecular orbital (HOMO) energy level. As a result, the SGT-137-based DSSC exhibits a higher PCE (12.45%) than that based on SGT-130 (9.83%) owing to the improvement of current density and retardation of charge recombination by the hexyl substituted TI unit. These results indicate that the TI moiety is a good candidate for remarkable π-electronic mediators in D–π–A organic sensitizers with the characteristic of facile synthesis compared to other complicated π-bridges. Furthermore, the parallel-connected tandem device with SGT-137 and SGT-021 porphyrin-based DSSCs shows a significantly improved current density (22.06 mA cm−2) and PCE (14.64%), which is the highest value reported for organic-based tandem solar cells to date.
185 citations
TL;DR: The fusion of substituted methylene-bridged small aromatic ring to a porphyrin core would overcome these drawbacks, boosting the cell performance and reboot the exploration of aromatic-fused porphirin sensitizers for high-performance DSSCs.
Abstract: Over the last decades, porphyrin sensitizers have made a remarkable contribution to performance improvement in dye-sensitized solar cells (DSSCs). In particular, versatile push–pull-type porphyrin sensitizers have achieved power conversion efficiencies (η) over 10% as a result of their improved light-harvesting abilities. Meanwhile, aromatic ring fusion to a porphyrin core is an attractive option for highly efficient DSSCs because of its expanded π-conjugation and resultant red-shifted absorption. Nevertheless, aromatic-fused porphyrin sensitizers have suffered rather low cell performances due to their mismatch of HOMO–LUMO levels, high aggregation tendency, and short lifetime of the excited states. Bearing these in mind, we envisioned that the fusion of substituted methylene-bridged small aromatic ring to a porphyrin core would overcome these drawbacks, boosting the cell performance. Herein, we report a series of substituted methylene-bridged thiophene-fused porphyrins, AfZnP, DfZnP, and DfZnP-iPr. After...
160 citations
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TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
26,457 citations
TL;DR: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency as mentioned in this paper, and many DSC research groups have been established around the world.
Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...
8,707 citations
TL;DR: In this article, a Co(II/III)tris(bipyridyl)-based redox electrolyte was used in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8).
Abstract: The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co(II/III)tris(bipyridyl)–based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.
5,462 citations
Journal Article•
TL;DR: Mesoscopic solar cells that incorporate a Co(II/III)tris(bipyridyl)–based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer are reported, enabling attainment of strikingly high photovoltages approaching 1 volt.
Abstract: Simultaneous modification of the dye and redox shuttle boosts the efficiency of a dye-sensitized solar cell. The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co(II/III)tris(bipyridyl)–based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.
5,385 citations
TL;DR: A review with 156 refs on interfacial electron transfer reactions in colloidal semiconductor solns and thin films and their application for solar light energy conversion and photocatalytic water purifn is presented in this paper.
Abstract: A review with 156 refs. on interfacial electron transfer reactions in colloidal semiconductor solns. and thin films and their application for solar light energy conversion and photocatalytic water purifn. Some of the topics discussed include; optical and electronic properties of colloidal semiconductor particles, quantum size effects in the photoluminescence of colloidal semiconductors, light-induced charge sepn., dynamics of interfacial charge transfer processes, properties and prepn. of nanocryst. semiconductor electrodes, energetics and operations of the nanoporous solar cell.
5,065 citations